This invention pertains to the art of gripper assemblies and actuators therefor, and more particularly to grippers for selectively handling sheet products such as newspapers.
The invention is particularly applicable to a gripper having opposed clamping jaws selectively brought into a closed position and spring biased to an open position upon actuation of a release arm. The invention will be described with particular reference to this embodiment; however, it will be appreciated that the invention has broader applications and may be advantageously employed in actuating related grippers for gripping other products if so desired.
Typically, an article conveyor apparatus for handling sheet products such as newspapers and the like includes a plurality of grippers spaced along an endless chain. Each gripper is adapted to convey an individual newspaper from one work station to another. Each gripper includes first and second clamping jaws initially disposed in spaced relation and adapted for receipt of a newspaper therebetween. At a pickup station, an edge of the newspaper is inserted between the clamping jaws and the clamping jaws then move relative to one another to tightly grip the newspaper for advancement with the endless chain. Each newspaper can thus be handled individually and for further processing or operational steps downstream. At a release or dropoff station, a release lever or arm is engaged by an actuating mechanism to move the release arm to an actuated or opening position thereby permitting the clamping jaws to open relative to one another and release the newspaper from further gripping. For example, the clamping jaws are normally biased to an open position by a spring. When the clamping jaws are closed, energy is stored in the spring while a wrap spring clutch prevents the jaws from opening. The actuating mechanism releases the wrap spring clutch and the energy stored in the spring opens the clamping jaws.
Structures of this type are generally well known in the art as represented by U.S. Pat. No. 4,381,056 to Eberle issued Apr. 26, 1983. As disclosed in the noted patent, a roller surface is selectively moved into the path of the gripper, particularly the release arm, for abutting, physical engagement therewith. This moves the release arm to a detent release or actuated position so that the clamp jaws may be urged to an open position.
Use of a piston or other mechanical member to contact the release arm is conventional in the art. The extremely large number of newspapers or other sheet products being handled and the repetitive use of grippers due to the endless conveyor chain arrangement imposes a great deal of wear and tear on the physical structure of the processing system. The continuous physical contact between the mechanical actuator, typically an air cylinder, and the release arm of the gripper requires replacement of the air cylinder approximately every three to six months under normal operating conditions. Speed of operation is also a constraint with a piston/cylinder arrangement. Moreover, even though the grippers are manufactured for ease of removal from the conveyor chain, servicing or replacement of the mechanical actuating arrangement still constitutes a great deal of down time and unnecessary labor. Thus, either the actuating assembly and/or the grippers are exposed to degradation as a result of the physical contact necessary to release the gripper from a clamped engagement.